1. Field of the Disclosure
The present disclosure relates to mobile terminals provided with antennae. In particular, the present disclosure relates to a casing connecting structure that reduces degradation of receiver sensitivity and so forth caused by an antenna current in the mobile terminal that includes first and second casings.
2. Description of Related Art
Presently, some mobile phone terminals in the market are provided with first casings (lower casings) that include display devices such as liquid crystal displays (LCDs) and second casings that include input devices such as tenkeys. In such a mobile phone terminal, one of the first and second casings is slidably connected to the other casing so as to be openable and closable (for example, see Patent Literature 1).
To date, flexible printed circuit boards are used to electrically connect casings relatively movable to each other as described above. Typically, one of the casings is provided with at least one antenna device in order to transmit and receive wireless signals.
To date, the following problems are caused with wireless communication mobile terminals provided with such flexible printed circuit boards (hereinafter abbreviated to FPCs).
The first problem is degradation of receiver sensitivity in a mobile terminal provided with a system that simultaneously performs transmission and reception (for example, CDMA) or in a mobile terminal provided with a plurality of systems in which transmission or reception of the plurality of the systems may be simultaneously performed (for example, long term evolution (LTE) and Bluetooth (registered trade mark)).
For example, a transmission antenna current (high-frequency current) may be introduced into the FPC with low-frequency signals, clock signals, noise, and so forth through the FPC. When such an antenna current is input to an integrated circuit (IC), which is a nonlinear element connected to this FPC, it may cause the nonlinear element to generate receive band noise. The generated noise is introduced into the antenna of a system through space and conductors, thereby degrading receiver sensitivity.
Also in this case, the nonlinear element may generate spurious signals, which may affect surrounding electronics.
Furthermore, when the transmission antenna current is input to a circuit connected to the FPC through the FPC, the circuit may malfunction. For example, in a system in which high-power transmission is performed such as GSM, the transmission antenna current may cause an LCD driver to malfunction, thereby shaking contents displayed on the LCD. A control circuit of an LCD back light may malfunction, thereby flickering contents displayed on the LCD.